/*
 * Copyright (C) 2012 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.util.concurrent;

import static org.mockito.Answers.CALLS_REAL_METHODS;
import static org.mockito.Mockito.doReturn;
import static org.mockito.Mockito.mock;

import com.google.common.base.Function;
import com.google.common.collect.ForwardingObject;
import com.google.common.collect.Iterables;
import com.google.common.testing.ForwardingWrapperTester;
import java.lang.reflect.Method;
import java.util.Arrays;

/**
 * Tester for typical subclass of {@link ForwardingObject} by using EasyMock partial mocks.
 *
 * @author Ben Yu
 */
final class ForwardingObjectTester {

    private static final Method DELEGATE_METHOD;
    static {
        try {
            DELEGATE_METHOD = ForwardingObject.class.getDeclaredMethod("delegate");
            DELEGATE_METHOD.setAccessible(true);
        } catch (SecurityException e) {
            throw new RuntimeException(e);
        } catch (NoSuchMethodException e) {
            throw new AssertionError(e);
        }
    }

    /**
     * Ensures that all interface methods of {@code forwarderClass} are forwarded to the
     * {@link ForwardingObject#delegate}. {@code forwarderClass} is assumed to only implement one
     * interface.
     */
    static <T extends ForwardingObject> void testForwardingObject(final Class<T> forwarderClass) {
        @SuppressWarnings("unchecked") // super interface type of T
        Class<? super T> interfaceType =
                (Class<? super T>) Iterables.getOnlyElement(Arrays.asList(forwarderClass.getInterfaces()));
        new ForwardingWrapperTester().testForwarding(interfaceType, new Function<Object, T>() {
            @Override
            public T apply(Object delegate) {
                T mock = mock(forwarderClass, CALLS_REAL_METHODS.get());
                try {
                    T stubber = doReturn(delegate).when(mock);
                    DELEGATE_METHOD.invoke(stubber);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }
                return mock;
            }
        });
    }
}
